Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$126.54	9.254%	$138.25	$138.25	$138.25	$138.30
Purchase #2	$54.91	12.451%	$61.7468	$61.75	$61.75	$61.70
Purchase #3	$5.51	5.740%	$5.8263	$5.83	$5.85	$5.80
Purchase #4	$114.63	5.360%	$120.7742	$120.77	$120.75	$120.80
Purchase #5	$66.60	9.441%	$72.8877	$72.89	$72.90	$72.90
Purchase #6	$203.40	8.432%	$220.5507	$220.55	$220.55	$220.60
Purchase #7	$95.83	4.133%	$99.7907	$99.79	$99.80	$99.80
7 purchase totals =	$667.42		$719.8264	$719.83	$719.85	$719.90